Modern tools and manipulating instruments, especially instruments with jaws for performing surgical operations, such as cutting, grasping and holding, are providing increasing levels of functionality and strength to support modern needs including applications in minimally invasive and micro-surgery.
Often, the tools available are not efficient in applying the correct amount of force precisely or being precisely positioned. As surgical instruments decrease in size, a number of problems occur with mechanisms having jaws, such as forceps, graspers, and scissors.
New surgical techniques have created less invasive procedures, such as minimally invasive surgery (MIS) and robotic MIS, which has created the need for smaller diameter instruments. The need for small instruments is motivated by patient concern for cosmetic healing with minimal or no scars and less incision size related post-operative pain.
The development of less invasive medical instruments is also motivated by surgeons who need smaller instruments to address smaller anatomy such as small blood vessel and nerve re-anastomosis, ophthalmic surgery, vasectomy reversal and the like. Another surgeon motivation for developing less invasive medical instruments and procedures is the desire to make patients happy with less noticeable scarring, less post-operative pain and more rapid healing.
One of the technical obstacles to producing these less invasive medical instruments is the transmission of force from the mechanical actuator to the instrument jaw or end effector on the other end. The delivery of too much force or too little can present a surgeon with additional unwanted complications in surgery.
Another difficulty is the precise positioning and movement of the medical instrument jaws or end effector. Providing a precise control through a system of linkages can be difficult. The combined linkages have inherent movement error called “hysteresis”, which is usefully thought of as lost motion or wasted energy. The hysteresis of a medical instrument is caused by the friction between moving parts, and the stretching of interconnecting parts.
Block and tackle style mechanisms for jaw actuation can provide greater mechanical advantage to the actuating cable but add to parts count, assembly cost, and mechanism friction.
The need to reduce costs, to improve efficiencies and performance, and to meet competitive pressures adds an even greater urgency to the critical necessity for finding answers to these problems. Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.